1. Technical Field
This invention concerns a traction-type elevator in which the cage of the elevator moves vertically under the traction of a rope winding hoister.
2. Description of the Prior Art
FIGS. 4-6 show a conventional traction-type elevator. As shown in the FIGS. 4 and 5, a cage (101) is movable vertically in an elevator shaft (102). A pair of cage sheaves (104, 105) is mounted via a cage frame (103) on the upper portion of the cage (101). That is, the cage sheaves (104, 105) are arranged in a support beam (107); see FIG. 5. In the support beam (107), a hanging rod (108) is arranged. The hanging rod (108) is mounted on the cage frame (103) via spring washers (113) and multiple torsion coil springs (114). Each of the multiple torsion coil springs (114) is contained in upper/lower cases (or housings) (115a, 115b) so that each torsion coil spring (114) does not escape from between the spring washers (113) and the cage frame (103).
Multiple turns of a rope (106) are hung on the cage sheaves (104, 105). The rope (106) is also hung on a driving sheave (110) of a hoister (109) which includes, e.g., a motor. One end of the rope (106) is attached to an overhead beam (111), and the other end is attached to a counterweight (112); see FIG. 4.
The diameters of the sheaves (104, 105) are determined from the legally determined diameter of the rope (106). Consequently, when the sheaves (104, 105) become larger, as shown in FIG. 6, it becomes impossible to arrange said sheaves (104, 105) along the cage frame (103). Instead, the sheaves (104, 105) are arranged at an angle with respect to frame (103); that is, in the diagonal direction of the cage (101). On the angled sheaves (104, 105), multiple turns of the rope (106) are wound; they are also wound on the driving sheave (110) above the sheave (104).
Because the sheaves (104, 105) are arranged in the diagonal direction of the cage (101), there is a small twist for the overall rope (106) wound on the driving sheave (110) from the cage sheave (104). In particular, when the cage (101) moves to the upper floors, the twist of the rope (106) is increased.
As the rope (106) is pulled by the driving sheave (110) to move the cage vertically, a vibration is generated by the twist of the rope (106).
In addition, when an end (106a, FIG. 4) of the rope (106) attached to the overhead beam (111) deviates slightly with respect to the cage sheave (104), the vibration becomes larger. However, transmission of the vibration generated to the cage (101) can be prevented by using multiple torsion coil springs (114) arranged between the support beam (107) and the cage frame (103).
As explained above, for the conventional traction-type elevator, when the cage (101) moves to the upper floors, the twist of the rope (106) is increased, the support beam (107) rotates slightly, and the support beam (107) deviates slightly with respect to the cage frame (103). Consequently, the upper case (115a) and the lower case (115b) are pressed against each other, and the vibration-proof effect of the torsion coil springs (114) is hampered.
As the twist of rope (106) is increased, in order to reduce the twist, the support beam (107) is rotated slightly with respect to the cage frame (103).
However, if the support beam (107) can be rotated somewhat to alleviate the aforementioned twist, the vibration generated can be suppressed somewhat. However, as pointed out above, the support beam (107) cannot be rotated significantly because of the presence of the cases (115a, 115b); thus, the vibration generated cannot be suppressed at all.